This research proposal uses tightly controlled feeding and exercise conditions to extend classical observations of this Laboratory on dietary effects on blood lipids and metabolic effects of exercise. Twenty-four healthy but mildly to moderately overweight college men will receive meals and supervised group walking on a 457 cm x 152 cm treadmill in the Laboratory facilities. Lipid determination performed in the Minnesota Core LRC Laboratories will include total plasma cholesterol, triglycerides, and phospholipids, and their levels in HDL, LDL, and VLDL. Concentration of HDL subclasses and apolipoproteins will also be regularly determined. After 3 weeks on a control "house diet", subjects will be randomized to 1 of 4 groups for a 12-week study period as follows: Group 1 will continue to receive the control diet; Group 2 will have a reduction in dietary calories of 500 kilocal/day followed by a 3 week period of weight stabilization at the reduced level by increasing caloric intake; Group 3 will perform 500 kilocal/day of treadmill walking (1 hour daily at 3.0 mph at 10% grade with an adjustment in caloric intake to maintain weight, followed by a 3 week detraining period; and Group 4 will perform a similar amount of exercise with no caloric adjustment, followed by a 3 week weight stabilization period by increasing caloric intake. After a 13 week recovery period, the experiments will be repeated with Groups 1 and 2 and Groups 3 and 4 switching interventions. Comparisons will be made between group lipid changes associated with walking exercise with and without weight loss and between groups losing weight by caloric restriction, vs. exercise, before and after weight stabilization. Fourteen subjects have successfully completed the initial phase of the study and a group of twenty-four are currently in progress in phase 2.